In the 3rd Generation Partnership Project (3GPP) radio access network 1 (RAN 1) meeting #87, it is determined that a polar coding scheme is used for both uplink control information and downlink control information of an enhanced mobile broadband (eMBB). To improve polar decoding performance, an outer code having a check capability may be cascaded outside the polar. Currently, cascaded outer codes are classified into a cyclic redundancy check (CRC) code and a parity check (PC) code. A scheme in which the CRC code is used as an outer code is referred to as CRC-aided polar (CA-Polar), and a scheme in which the PC code is used as an outer code is referred to as PC polar.
The CA-polar scheme is as follows: On an encoding side, a subchannel of a frozen bit and a subchannel of an information bit are determined, bits that need to be transferred on the subchannel of the frozen bit and the subchannel of the information bit are determined, and then polar encoding is performed on all the bits. A bit transferred on the subchannel of the frozen bit may be a bit 0 or an agreed bit, and the bit transferred on the subchannel of the information bit may include an information bit and a CRC bit. On a decoding side, a CRC is performed on decoding values of a plurality of paths of a decoder, and a path on which the CRC succeeds is used as a decoding output result. The PC polar scheme is as follows: On an encoding side, subchannel of a frozen bit, a subchannel of a PC frozen bit, and a subchannel of an information bit are determined, bits that need to be transferred on the subchannel of the frozen bit, the subchannel of the PC frozen bit, and the subchannel of the information bit are determined, and then polar encoding is performed on all the bits. A bit transferred on the subchannel of the frozen bit may be a bit 0 or an agreed bit, the bit transferred on the subchannel of the PC frozen bit is a PC frozen bit, and the bit transferred on the subchannel of the information bit is an information bit. On a decoding side, a PC bit is distributed among information bits. In a middle stage of decoding, the PC bit may be used to provide an early termination. To be specific, if a decoding error occurs in any path when a decoding process is executed, the decoding process of the path is interrupted and the path is deleted, so that a path on which PC decoding succeeds is determined in a plurality of paths of the decoder. Currently, a simplified PC polar scheme is proposed, and is referred to as a simplified PC (Simplified PC-Polar, Sim-PC). In the Sim-PC scheme, a quasi-periodic feature of channel polarization is used; each period is used as a segment, and the PC frozen bit is selected in advance in each segment to simplify construction of the PC polar.
However, in the CA-polar, the CRC bit is cascaded at an end of information bits. Therefore, a check is performed after the information bits are decoded, and consequently, the CA-polar does not provide a capability of determining an early termination during decoding. In addition, the CRC bit always occupies a subchannel having highest reliability, and no enough space is left for encoding optimization, resulting in poor performance on the encoding side. A construction method of the PC polar is relatively complex, and a decoding result of a first path is output by default. However, an error may occur in the decoding result of the first path, resulting in poor performance on the decoding side. Performance of the Sim-PC is similar to that of the PC polar. FIG. 1 shows a comparison of block error rate (BLER) performance between the Sim-PC and the PC polar (referred to as PC for short in FIG. 1) when there are 120 information bits. In FIG. 1, cases in which lengths after encoding are 720 (120/720), 240 (120/240), and 360 (120/360) are included. At a signal-to-noise ratio, a lower block error rate indicates higher transmission reliability of a method at the signal-to-noise ratio. If a block error rate curve of a method drops more quickly (a slope becomes higher) with rising of the signal-to-noise ratio, it indicates that the method can reach higher transmission reliability more quickly with rising of the signal-to-noise ratio. It can be learned that, the Sim-PC has a slight performance loss in a high signal-to-noise ratio range at the decoding side.